The Effects of Damming on River Herring Spawning Habitat in the Kennebec, Penobscot and St. Croix Watersheds of Maine

The damming of coastal rivers has obstructed the upstream migration of anadromous fish for centuries, diminishing the habitat available for their reproduction. The Kennebec, Penobscot and St. Croix rivers, which historically hosted tens of millions of spawning river herring every spring, have been dammed in close proximity to their tailwaters. Restoration projects have helped reconnect lower reaches of the Kennebec and Penobscot to the ocean, while the St. Croix is still dammed in close proximity to its tailwaters. GIS was used to maps the current and virgin stream and lake habitat available to river herring in the Kennebec, Penobscot and St. Croix watersheds. Results show that approximately 12% of the virgin stream spawning habitat along the Kennebec and Penobscot remains unimpeded by dams, while only 1.5% of the virgin stream habitat along the St. Croix is below initial dams. Fish passageways have helped mitigate the damage to fish runs caused by dams, but dam removal is the most effective river restoration method. Along the St. Croix the Milltown dam near the head of tide is the subject of a removal proposal that could help repair the ecological damages to the watershed caused by damming and laws that once prohibited the passage of migratory fish upstream